在DataGrid的头中插入CheckBox单选框定义为全选并实现整个DataGrid的每行数据前的CheckBox全选

在DataGrid的绑定时间里写如下代码：
   if(e.Item.ItemType == ListItemType.Header)
   {
        CheckBox chk = (CheckBox)e.Item.FindControl("chkAllServer");
        // 给页眉上的CheckBox添加出发事件
        chk.CheckedChanged +=new EventHandler(chk_CheckedChanged);
   }

private void chk_CheckedChanged(object sender, System.EventArgs e)
  {
       CheckBox chk = this.GetHeaderCheckBox(this.DataGrid1);
       foreach (DataGridItem i in this.DataGrid1.Items)
       {
            CheckBox inChk = (CheckBox)i.FindControl("chkDelServer");
            inChk.Checked = chk.Checked;
       }
  }
//得到指定DataGrid的题头的CheckBox对象
  private CheckBox GetHeaderCheckBox(DataGrid grd)
  {
       CheckBox chk = null;
       foreach (DataGridItem i in grd.Controls[0].Controls)
       {
            if(i.ItemType == ListItemType.Header)
            {
                 chk = (CheckBox)i.FindControl("chkAllServer");
                 break;
            }
       }
       return chk;
  }